1. Field of the Invention
The present invention relates to a hub for the rotor head of a rotary-wing aircraft, as well as to a rotor head including such a hub.
2. Description of the Related Art
A hub for the rotor head of a rotary-wing aircraft is already known from French patent FR-A-2 671 049, the rotor comprising at least two blades each of which is linked radially to said hub by a blade root provided with a rigid loop constituting the attachment of the blade onto said hub, said hub carrying laminated spherical stops, each of which is associated with one blade and comprises, between an outer armature rigidly linked to said hub and an inner armature linked to the root of said blade, an alternating stack of rigid cups and layers of an elastic material in the form of spherical portions having a common center, each laminated spherical stop, for the associated blade, constituting an element for retaining on said hub and a single articulation in flapping, drag and pitch, and said rigid loop of a blade surrounding the associated laminated spherical stop and being integral with the inner armature of this latter stop.
In the above document, said hub takes the form of a single-piece cage provided with a thin sidewall, of substantially cylindrical shape, including at least as many apertures as there are blades, each aperture having dimensions which are sufficient for at least the passage and the flapping of the laminated spherical stop of the corresponding blade.
Hence, with such a known hub, in the production of the rotor head, it is necessary to integrate each spherical stop of a rigid loop with the associated blade, then to insert the stops, thus integrated with their blades, through said apertures into said cage and, finally, to fix the stops to the hub. It can easily be imagined that this gives rise to difficult handling, adjustment and assembly operations.
In order to facilitate these operations, thought has already been given to providing intermediate linking sleeves between said stops and said blades, each of said sleeves, at one end, carrying the rigid loop, and, at the other end, carrying fixing means for the root of a blade. Hence, the blades can be mounted on the rotor head only after the linking sleeves have been mounted in the hub, which facilitates the complete mounting of the rotor head, but entails the supplementary components which are said linking sleeves.